Photographic colloid transfer system



United States Patent 3,340,063 PHOTGGRAPHIC COLLOID TRANSFER SYSTEM Norman W. Kalenda, Rochester, N.Y., assignor to Eastman Kodak Company, Rochester, N.Y., a corporation of New Jersey No Drawing. Filed Sept. 4, 1963, Ser. No. 306,627 13 Claims. (CI. 96-95) This invention relates to colloid transfer photographic materials, more particularly to light-sensitive materials which are suitable for roomlight handling.

In the photographic colloid transfer system, as described in Yutzey et al. US. Patents 2,596,756 and 2,716,059, an unhardened silver halide photographic emulsion containing a tanning developer is exposed to an image and after sufficient development, the developing silver halide emulsion is pressed against a surface to transfer a stratum of the gelatin layer to the receiving surface. In this way a positive image is obtained of the exposed image.

In one commercial embodiment of colloid transfer, the silver halide emulsion used for ofiice copying purposes is handled in roomlight so that there is a need for adding a substance to the emulsion which acts to reduce the emulsion speed to a level which will permit handling in average roomlight, such as fluorescent light, rich in blue light, but fast enough for imagewise exposure in suitable exposing equipment using incandescent lamps.

Methylene blue has been proposed for this purpose. However, methylene blue has not been entirely satisfactory since it interferes with certain spectral sensitizers causing a loss in sensitized speed which is reflected in increased exposure being required. In some instances, the incoporated developer causes the emulsion containing methylene blue to become resensitized both to the printing light and to roomlight. Moreover, there is a limited desensitization possible with methylene blue, since the desensitization approaches a maximum asymptotically as the concentration is increased.

It has been desirable to find a substitute for methylene blue in the unhardened colloid transfer type emulsions which contain tanning type silver halide developers which would overcome the disadvantages of methylene blue. However, such a desensitizer needs to be stable to provide for good keeping. It needs to be inert to the incorporated developers in the emulsion and to be compatible with the silver halide emulsions. In addition, the desensitizer should not interfere with spectral sensitization of the emulsion nor should it interfere. with the tanning action of the developer on a colloid such as gelatin in the exposed non-image areas so that poor transfers result.

I have found that certain heterocyclic N-oxide desensitizers can be used to densensitize colloid transfer emulsions free from interfering with the spectral sensitivity of the emulsion and the tanning effect of the incorporated tanning developer.

One object of this invention is to provide an unhardened silver halide emulsion containing a densensitizer which permits roomlight handling of the emulsion without seriously reducing its sensitivity to the printing light. A further object is to provide a densensitzer which does not interfere with the spectral sensitivity of a colloid transfer silver halide emulsion. An additional object is to provide a densensitizer for silver halide emulsions having incorporated therein a tanning silver halide developer without interfering with the tanning action of the developer.

The above objects are attained by incorporating in the emulsion at least one N-oxide of 4-nitropyridine or 4- nitroquinoline. Other useful compounds include the N- oxides of heterocyclic compounds, for example, pyridine,

3,340,063 Patented Sept. 5, 1967 ice quinoline, isoquinoline, thiazole, benzthiazole, oxazole, benzoxazole, naphthathiazole, napthoxazole, benzo-2,1, 3-oxanaphthazole, pyrimidine or quinazoline. These compounds may be prepared by nitrating a heterocyclic compound of which the nitrogen atom or at least one of them, if more than one of them is present, is in the form of an N-oxide. These compounds may also be prepared by treatment of an N-heterocyclic compound with a peracid.

A useful method of incorporating the desensitizer is to dissolve the desensitizer in a small amount of a watermiscible solvent such as, for example, acetone, methanol, ethanol, etc.

In our preferred embodiment 0.5 to 3 grams of the desensitizer per mole of silver halide are added to a substantially unhardened colloid silver halide emulsion containing a tanning silver halide developer.

Although our preferred emulsion is a silver chloride emulsion, other silver halide emulsions can be used. including silver bromide, silver iodide, silver chlorobromide, silver chloroiodide, silver bromoiodide, and silver chlorobromoiodide. Mixtures of these may also be used.

The tanning developers which may be used are those disclosed in the above US. patents describing colloid transfer emulsions. In addition, non-tanning silver halide developers may be incorporated in the emulsions as described in the above patents or used in the developing solution to improve the density of the transferred image.

The colloid transfer emulsions of this invention may also be used to prepare lithographic plates and the emulsions of this invention may be exposed either by the reflex method or through appropriate optical systems depending upon the speed of the emulsion used, the desired result, etc.

The concentration of the tanning developing agent in the emulsion is dependent in part upon the result desired, but can be of the order of 350 grams of tanning developer agent per kilogram of silver nitrate converted to silver halide, used in making the emulsion, to obtain good den sity or about 250 grams per kilogram of silver nitrate to obtain adequate density and an emulsion having optimum keeping properties. i

The emulsion layer used in this process can be dispersed in a colloid vehicle such as gelatin or a resin such as polyvinyl alcohol or polyacrylamide, capable of being differentially tanned.

It is necessary for the successful operation of the invention that the emulsion layer be not harder than would be the case with gelatin containing 0.25 ounce of formaldehyde (40 percent diluted 1:3 with water); or 0.7 gram of dry formaldehyde per pound when freshly coated; or 0.1 ounce of the solution per pound for a sample aged 3 to 6 months. By substantially unhardenedias used herein, and in the appended claims, it is to be understood that this means a hardness of the order obtained with formaldehyde treated gelatin under the conditions above.

A substantially unhardened gelatino-silver halide emulsion containing 1 mole of silver chloride, 300 grams of gelatin and 5700 grams of water is gelled, noodled and washed for one-half hour with water, then melted at 40 C., and the following addition made:

650 grams of 8 percent aqueous saponin,

600 grams of a dispersion of 4-phenylcatechol prepared by dissolving 50 grams of 4-pheny1catechol in 70 grams of dibutyl phthalate at C. and pouring it into a vigorously stirred solution of 50 grams of gelatin in 50 grams of 8 percent aqueous saponin solution and 500 cos. of water at 40 C.

To this emulsion is added a green sensitizing mecrocyanine dye, and to each sample to be tested, a desensitizer in an amount as shown in the table below. The desensi tizer is dissolved in a small amount of methanol. The emulsion is coated at 190 mg. of silver per square foot on a paper support and dried.

The following desensitizers were used in the above emulsions:

DESENSITIZERS I. Methylene blue II. 4-nitropyridine-N-oxide III. 4-nitro-2-picoline-N-oxide IV. 4-nitroquinoline-N-oxide V. 4 nitro-6-chlorobenzotriazole VI. 2,4-diphenyl-6-( 1-butyl-4-p-dimethylaminophenyl-1 ,3-

butadienyl)pyry1ium fluoroborate The following results were obtained by testing with light, which simulated 'blue light, and also with white light in which the blue light had been removed. The test using the Wratten No. 4 Filter indicates the response of the emulsion to white light which has the blue light removed. The test using the Wratten No. 35 and 38A filters shows the response to white light in which all of the wave lengths in the spectrum have been removed except for the blue light.

The coatings in each instance were exposed on a Verifax Regent Copier to incandescent light for 20 seconds, immersed for 60 seconds in an activator solution having the following composition:

Grams Na CO H2O Urea 50 Water to 1V liter.

held at a temperature of 81 F. and rolled in contact with the Verifax matrix paper.

Coating 82 showed about 2 /2 times the printing speed of coating 80 but equal or similar roomlight tolerance. Coatings 05' and showed and twice the printing speed, respectively, of coating 99 with five and three times, respectively, the tolerance to roomlight exposure. There was no appreciable change in contrast.

Similar results are obtained by the use of any other of the compounds listed above, used in similar quantity.

a mole of silver halide.

The invention has been described in detail with particular reference to preferred embodiments thereof, but it Will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A substantially unhardened hydrophilic colloid silver halide emulsion containing a colloid tanning silver halide developing agent and a desensitizing amount of a desensitizing compound which is a nitro derivative of a heterocyclic compound selected from the class consisting of pyridine, quinoline, isoquinoline, thiazole, benzothiazole oxazole, benzoxazole, naphthothiazole, naphthoxazole, benzo-2,l,3-oxadiazole, pyrimidine and quinazoline, and wherein at least one hetero nitrogen atom is in the form of an N-oxide.

2. An emulsion of claim 1 in which the colloid is gelatin.

3. An emulsion of claim 1 in which the desensitizing compound is present in an amount of 0.5 to '3 grams per mole of silver halide.

4. An emulsion of claim 1 in which the colloid is gelatin and the desensitizing compound is contained in an amount of 0.5 to 3 grams per mole of silver halide.

5. An emulsion of claim 1 in which the desensitizing compound is a nitro derivative of a pyridine-N-oxide.

6. An emulsion of claim 1 in which the desensitizing compound is a nitro derivative of a picoline-N-oxide.

7. An emulsion of claim 1 in which the desensitizing compound is a nitro derivative of a quinoline-N-oxide.

8. An emulsion of claim 1 in which the desensitizing compound is 4-nitr0py'ridine-N-oxide.

9. An emulsion of claim 1 in which the desensitizing compound is 4-nitro-2-picoline-N-oxide.

10. An emulsion of claim 1 in which the desensitizing compound is 4-nitroquinoline-N-oxide.

11. An emulsion of claim 1 in which the desensitizing compound is 4-nitropyridine-N-oxide which is contained in the emulsion in an amount of 0.5 to 3 grams per mole .of silver halide.

12. An emulsion of claim 1 in which the desensitizing compound is 4-nitro-2-picoline-N-oxide which is contained in the emulsion in an amount of 0.5 to 3 grams per 13. An emulsion of claim 1 in which the desensitizing compound is 4-nitroquinoline-N-oxide which is contained in the emulsion in an amount of 0.5 to 3 grams per mole of silver halide.

References Cited UNITED STATES PATENTS 2,716,059 8/ 1-955 Yutzy et a1. "a 96-95 3,050,395 8/ 1962 Duflin 96-l01 J; TRAVIS BROWN, Primary Examiner. N RM N G- QRCH N; Exami e 

1. A SUBSTANTIALLY UNHARDENED HYDROPHILIC COLLOID SILVER HALIDE EMULSION CONTAINING A COLLOID TANNING SILVER HALIDE DEVELOPING AGENT AND A DESENSITIZING AMOUNT OF A DESENTISITIZING COMPOUND WHICH IS A NITRO DERIVATIVE OF A HETEROCYCLIC COMPOUND SELECTED FROMT EH CLASS CONSISTING OF PYRIDINE, QUINOLINE, ISOQUINOLINE, THIAZOLE, BENZOTHIAZOLE OXAZOLE, BENZOXAZOLE, NAPPTHOTHIAZOLE, NAPHTHOXAZOLE, BENZO-2,1,3-OXADIAZOLE, PYRIMIDINE AND QUINAZOLINE, AND WHEREIN AT LEAST ONE HETERO NITROGEN ATOM IS IN THE FORM OF AN N-OXIDE. 